Crosslinked polymeric materials have long been known as useful binders for electrostatographic toners. Various types of crosslinked polymers, including vinyl, styryl, and acrylic resins, as well as condensation polymers such as polyesters are disclosed in U.S. Pat. No. 3,938,992 and in Reissue Patent No. 31,072.
Other references describing toners formed from crosslinked polyesters include the following, the disclosures of which are incorporated herein by reference:
U.S. Pat. No. 5,276,127, which describes a crosslinked polyester derived from at least one member selected from the group consisting of tribasic and tetrabasic acid components and trihydric and tetrahydric alcohol components and an aromatic or alicyclic diol component in which at least one of the hydroxyl groups is a secondary group.
U.S. Pat. No. 5,486,444, which describes a process for preparing a crosslinked polyester by first forming a polyhydroxy functional polyester resin precursor, which is then reacted with a dianhydride or diepoxy functional crosslinking component.
U.S. Pat. No. 5,789,527, which describes a polyester resin formed by linking crosslinked low-molecular weight polyesters through a dicarboxylic linking agent.
In addition to their usefulness for the production of toners, crosslinked polyesters have found extensive use in various other applications, for example, the production of thermosetting powder coating compositions. Such compositions are disclosed in, for example, U.S. Pat. No. 5,373,084, which describes the preparation of semicrystalline polyester plasticizers from crosslinkable resins and a variety of crosslinking agents. Among the types of crosslinking agents disclosed in this reference are hydroxyalkylamides, epoxy materials, glycouril compounds, and unblocked or blocked isocyanates.
Commercial polyester crosslinking chemistries frequently involve materials that are toxic or malodorous and, in addition, require in their preparation catalysts that may adversely affect the triboelectric performance of the toner particles. Furthermore, catalyzed processes often require an intimate knowledge of the materials and processes used by suppliers in the preparation of toner ingredient precursors. It would be highly desirable to have the ability to prepare crosslinked polyester toner binders using non-toxic, odorless, low cost ingredients under relatively mild conditions that do not require catalysts.